Drilling boreholes (e.g., for oil or natural gas wells) sometimes includes the use of drilling fluid, also known as “drilling mud.” Drilling fluid serves to provide counter-pressure against formation pressure as well as to lubricate the drill bit and carry cuttings for hole cleaning. Drilling fluid is typically pumped from a surface mud tank (or “mud pit”) down the drill pipe, so as to exit the drill bit at the end of the drill string. There, it provides its lubrication, sealing and cleaning functions. Thereafter, the drilling fluid flows up the annulus of the drill string and back to the surface. At the surface, the drilling fluid is cleaned of debris and returned to the reservoir, where it is re-used. Thus, drilling fluid flows in a loop, from the surface, to the bottom of the borehole, and back. This flow is referred to as drilling fluid “circulation.”
While it is normal to lose some drilling fluid in the circulation process, excessive lost drilling fluid is expensive in terms of unit mud costs (especially whole synthetic or low toxicity mineral oil mud) and non-productive time. It may pose safety related concerns, as drilling fluid is bulky, difficult to mix, difficult to store and excessive losses may reduce the counter balance effect against formation fluids. Thus, there is a need for diagnosing root cause(s) of, predicting, preventing and correcting, drilling fluid lost circulation events.